--- Makefile.in.orig	1993-04-03 07:12:15.000000000 +0800
+++ Makefile.in	2025-05-16 04:17:13.000000000 +0800
@@ -26,13 +26,13 @@
 #   -DEXTRACT_MACROS to use the macros EXTRACT_* (as opposed to
 #           the corresponding C procedures).  If not -DDEBUG, the macros
 #           are used.
-CPPFLAGS = 
+CPPFLAGS += 
 
 # Likewise, you can override CFLAGS to optimize, use -Wall, etc.
-CFLAGS = -g
+CFLAGS += -g
 
 # Ditto for LDFLAGS and LOADLIBES.
-LDFLAGS =
+LDFLAGS +=
 LOADLIBES =
 
 srcdir = @srcdir@